Description of problem:

When deleting a deep directory tree from two different instances of "rm -rf"
simultaneously, one of the instances may segfault.

Version-Release number of selected component (if applicable):

coreutils-5.97-12.3.fc6

Steps to Reproduce:
1. Create a deep directory tree (I used 10 levels deep)
2. From two different command lines, rm -rf the parent directory of the tree
3. Repeat (it requires tricky timing so may not always happen)
  
Actual results:

One of the 'rm's will segfault.

Expected results:

Neither of the 'rm's would segfault.

Additional info:

The problem seems to be in remove.c:remove_cwd_entries(), where opendir is
called on ".".  If this fails for reason of ENOENT, the function calls readdir
on the NULL dirp.

Patch attached.